The invention relates to a spray head for a sink faucet or the like that is suited for connection to a low-pressure storage tank (open hot-water storage tank), with a water feed, a normal jet discharge placed centrally in particular, a spray discharge placed in particular concentrically surrounding the normal jet discharge and having a multiplicity of small spray holes and a reversing valve, and in a normal position the reversing valve connects the normal jet discharge to the water feed and separates the spray discharge from the water feed and, in a spray position, connects the spray discharge to the water feed and separates the normal jet discharge from the water feed.
The known spray head on which the invention is based (IDEAL-STANDARD brochure "CERAMIX COMBI" W 538 2 S) is intended and suitable especially for a sink faucet, but a corresponding design of a spray head can also be used for other faucets, especially mixing faucets. It is essential here for such a spray head that it make operation possible with two types of jets namely, on the one hand, with a normal jet, on the other hand, with a spray jet. The normal jet exits at a normal jet discharge through a usual aerator or the like. On the other hand, the spray jet exits through a multiplicity of small spray holes of a spray discharge. In most cases, spray holes of the spray discharge are placed concentrically around the normal jet discharge.
If a known spray head explained above is connected to a central cold water storage and/or a warm water storage, there are no big connection problems. The same applies for connection to a flow heater. But with connection to a low-pressure storage tank, i.e., an open hot water storage tank, attention must be paid that the pressure in the low-pressure storage tank not rise at any time so high that a rupturing of the low-pressure storage tank is to be feared. The rupturing problem addressed here has become generally recognized for single-lever mixers and has lead to operation with permanently installed flow controls that keep the water flow constant even if the water pressure changes.
Regardless of the application of measures known in the art for preventing the rupturing of a low-pressure storage tank, it has turned out that with the use of the known spray head a danger of rupturing still exists when, with maximum flow rate of the water, the normal position is switched to the spray position. This rupturing problem peculiar to this spray head needs a solution, thus the teaching of the invention is based on the object of indicating a spray head fully suited for use in connection with a low-pressure storage tank.
The object indicated above is achieved in the spray head on which the invention is based in that a bypass pipe that operates in the spray position is placed in the reversing valve between the water feed and the normal jet discharge and in that the flow resistance of the bypass pipe is greater than the flow resistance of the spray discharge when the spray holes are not clogged, but the operationally maximum dynamic pressure produced upstream from the bypass pipe when the spray holes are clogged is smaller than the bursting pressure of an allocated low-pressure storage tank. Of course, because of the configuration according to the invention, such a spray head is completely suitable for connection to a low-pressure storage tank, but it can also likewise be used with sink faucets or the like connected in other ways. A first part of the invention lies in the recognition that the rupturing of a low-pressure storage tank during the above-explained switching to a spray head of the type in question can occur if the spray holes of the spray discharge are clogged completely or mostly by dirt or calcium deposits. On switching from the normal position with low flow resistance into the spray position, in this case there is a strong pressure impact, since the water flow is in effect suddenly blocked. Whether or not such a situation occurs can no longer be influenced by the manufacturer but rather depends only on the care with which the user keeps the spray holes of the spray discharge open. In view of the actual desire to achieve an effective switching between normal position and spray position, as a second part of the invention a further flow path has now been created for the spray position, a path that is always open and that can hardly be clogged normally with dirt or calcium deposits. By matching the flow resistance of this bypass pipe to the flow resistance of the spray discharge when the spray holes are not clogged, it is achieved according to the invention that, at most, a limited leak flow normally flows through the bypass pipe into the normal jet discharge. Even if it were to occur, this leak flow is not disturbing in practice. But on switching from the normal position into the spray position when the spray holes are clogged, the bypass pipe assumes entirely or to a large extent, from a flow viewpoint, the function of the spray discharge, even though, because of the higher flow resistance, at a higher pressure level than when the spray holes are not clogged. The flow resistance of the bypass pipe here is measured so that a pressure impact that can become dangerous, pressure-wise, for the low-pressure storage tank cannot occur.
Now there are various possibilities of configuring and further developing the teaching of the invention, for which purpose the following explanation of an embodiment based on the drawing can be referred to. In the drawing there are shown in: